Abstract

We present the blueprint for a novel negative-index metamaterial. This structure is fabricated via three-dimensional two-photon direct laser writing and silver shadow evaporation. The comparison of measured linear optical spectra with theory shows good agreement and reveals a negative real part of the refractive index at around 3.85μm wavelength—despite the fact that the metamaterial structure is bianisotropic owing to the lack of inversion symmetry along its surface normal.

Figures (3)

(a) Metamaterial design. The white regions are the polymer (SU-8) located on a glass substrate. The sidewalls of the polymer (encapsulated by SiO2 via ALD) are coated with silver. The polarization of the incident electromagnetic field is illustrated on the lower left-hand-side corner. (b) Oblique-view electron micrograph of a structure fabricated by direct laser writing and silver shadow evaporation that has been cut by a focused-ion beam (FIB) to reveal its interior. The complicated features visible underneath the glass-substrate surface are due to the FIB cutting and, hence, not relevant.

Measured linear-optical normal-incidence transmittance (red curve) and reflectance spectra of a structure similar to the one shown in Fig. 1b. Note that the reflectance taken from the air side Rair (blue curve) and that taken from the glass-substrate side Rglass (green curve) are distinctly different.